1. Field of the Invention
This invention relates to dicyclopentadiene polymers and more specifically it relates to dicyclopentadiene polymers having improved odor containing a deodorant.
2. Description of the Prior Art
U.S. Pat. No. 4,400,340 disclosed the formation of a thermoset polymer of dicyclopentadiene in a reaction injection molding (RIM) process by the use of an olefin metathesis catalyst and the disclosure of this patent is hereby incorporated by reference. Two reactive dicyclopentadiene (DCPD) monomer streams can be combined in a mix head to initiate polymerization, which takes place after injection into a mold. Part one of the two-part metathesis polymerization catalyst system comprises an aluminum alkyl, which can be pre-complexed with a Lewis base, such as an ether or ester, to control the induction time prior to onset of polymerization. Part two is a tungsten compound derived from tungsten hexachloride or tungsten oxytetrachloride.
The poly(dicyclopentadiene) (PDCP) thermoset formed in this way will typically contain levels of unreacted dicyclopentadiene monomer in the range of 0.1-3% by weight. Dicyclopentadiene monomer is characterized by a harsh, pungent, olefinic odor which is detectable at levels as low as 5 parts per billion (ppb) in air. Diffusion of dicyclopentadiene from the molded article imparts a noticeably unpleasant odor. This can be exacerbated when a molded article is trimmed exposing a cut rather than molded surface. Also, when parts are stored in sealed containers, such as shipping cartons, the atmosphere in the container takes on the odor of dicyclopentadiene.
Perfume additives are commercially available for many different plastics to impart a desirable odor to the product. For example, U.S. Pat. No. 3,926,655 disclosed a clear thermoplastic resin consisting essentially of a thermoplastic polyamide resin containing about 1 to 30% perfume oil and jewelry made thereof. The products so obtained give off a fragrant odor.
The perfume additives are generally esters, aldehydes or ketones (or mixtures thereof) having fruity, flowery, woody or other scents. They are used at levels in the parts per hundred range such that the odor of the plastic is masked and replaced with the odor of the perfume. At these levels, however, many perfume additives, especially those containing aldehydes or ketones, are incompatible with the PDCP catalyst system. They interfere with the formation of active catalyst and inhibit the polymerization. For example, at 0.5% fruity vanilla #61604 from S. S. Schoenmann, Inc. polymerization of dicyclopentadiene in test tubes did not occur in 5 minutes compared to 35 seconds for a control with no perfume. At lower levels (parts per million), they are ineffective in masking or neutralizing the odor of dicyclopentadiene. Other additives which are compatible at the high concentration range are ineffective perfumes or odor maskers. For example, limonene, which has a terpenic fragrance, can be added to dicyclopentadiene at a 10% level with no adverse effect on polymerization, but it does not noticeably improve the odor of molded PDCP articles.